Maternal glucose intolerance during pregnancy affects offspring POMC expression and results in adult metabolic alterations in a sex-dependent manner

Abstract

Introduction: Gestational diabetes (GDM) is associated with negative outcomes in mothers and their offspring, including greater risks of macrosomia at birth and the development of metabolic disorders. While these outcomes are well-established, the mechanisms by which this increased metabolic vulnerability is conferred on the offspring are comparatively lacking. One proposed mechanism is that maternal glycemic dysregulation alters the development of the hypothalamic regions related to metabolism and energy balance.

Methods: To investigate this possibility, in this study, we first examined the effects of STZ-induced maternal glucose intolerance on the offspring on pregnancy day (PD) 19, and, in a second experiment, in early adulthood (postnatal day (PND) 60). Whether effects would be influenced by sex, or exposure of offspring to a high-fat diet was also investigated. The impact of maternal STZ treatment on POMC neuron number in the ARC of offspring at both time points was also examined.

Results: As expected, STZ administration on PD 7 decreased maternal glucose tolerance, and increased risk for macrosomia, and loss of pups at birth. Offspring of STZ-treated mothers were also more vulnerable to developing metabolic impairments in adulthood. These were accompanied by sex-specific effects of maternal STZ treatment in the offspring, including fewer POMC neurons in the ARC of female but not male infants in late pregnancy and a higher number of POMC neurons in the ARC of both male and female adult offspring of STZ-treated dams, which was exacerbated in females exposed to a high-fat diet after weaning.

Discussion: This work suggests that maternal hyperglycemia induced by STZ treatment, in combination with early-life exposure to an obesogenic diet, leads to adult metabolic alterations that correlate with the increased hypothalamic expression of POMC, showing that maternal glycemic dysregulation can impact the development of hypothalamic circuits regulating energy state with a stronger impact on female offspring.

Keywords: POMC; gestational diabetes; glucose tolerance; hypothalamus; metabolic programming; pregnancy; streptozotocin.

Figure 1

Maternal oral glucose tolerance on pregnancy day 16. STZ administration in early pregnancy did not increase fasting glycemia (A), but increased glucose intolerance on PD 16 (B, C). Values expressed as mean ± standard error of the mean (Control N = 10; STZ N = 15). ***p<0.001.

Figure 2

The average number of POMC neurons in the Arc of female and male offspring on PD 19. Maternal hyperglycemia reduced the number of POMC neurons in the female offspring, but not in males. Values expressed as mean ± standard error of the mean (Females: Control N = 3, STZ N = 5; Males: Control N = 3, STZ N = 4). The images represent POMC staining in the Arc in all experimental groups. The scale in the first image (100 µm) is valid for all the images. **p<0.01.

Figure 3

Maternal outcomes at birth. Maternal hyperglycemia reduced litter size at birth (A), without changes in sex ratio (B). Both female and male offspring born to hyperglycemic dams showed increased body weight at birth (C), which was followed by a different distribution of pups classified asappropriate and large for pregnancy age in the hyperglycemic groups (D). Values expressed as mean ± standard error of the mean (Control N = 7; STZ N = 7). *p<0.05.

Figure 4

Female and male offspring body weight gain and caloric intake on PND 60. High-fat diet intake increased body weight gain and total caloric intake both in female (A, C) and male offspring (B, D). Increased body weight gain was also seen in male offspring born to hyperglycemic dams. Values expressed as mean ± standard error of the mean (Control N = 7; STZ N = 7). **p<0.01; ***p<0.001.

Figure 5

Female and male offspring fat deposition on PND 60. Despite no changes in female gonadal fat deposition (A), high-fat diet intake increased gonadal fat in males (B) and retroperitoneal fat deposition both in females (C) and males (D). Interestingly, maternal hyperglycemia decreased gonadal fat in males (B). Values expressed as mean ± standard error of the mean (Control N = 7; STZ N = 7). *p<0.05; **p<0.01; ***p<0.001.

Figure 6

Female and male offspring glucose tolerance on PND 60. High-fat diet intake after weaning increased fasting glycemia in females (A), but not in males (D), which was significantly impaired by maternal hyperglycemia. Also, high-fat diet exposure increased glucose intolerance in female and male offspring, as seen in the glycemic curve (B, E) and the AUC (C, F). Values expressed as mean ± standard error of the mean (Control N = 7; STZ N = 7). **p<0.01; ***p<0.001.

Figure 7

Average POMC neurons in female and male offspring on PND 60. Maternal hyperglycemia increased the number of POMC neurons in the Arc in both female (A) and male offspring (B). Interestingly, a high-fat diet intake after weaning increased POMC neurons only in females. Values expressed as mean ± standard error of the mean (Females: Control-chow N = 6; Control-HFD N = 6; STZ-Chow N = 7; STZ-HFD N = 6. Males: Control-chow N = 7; Control-HFD N = 6; STZ-Chow N = 6; STZ-HFD N = 5). The images represent POMC staining in the Arc in all experimental groups. The scale in the first image and inset (500 and 100 µm respectively) are valid for all the images. *p<0.05; **p<0.01.